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Correspondence: Mitra Mehrabani, Department of Pharmacognosy, Faculty of Pharmacy, Kerman University of Medical Sciences, Kerman, Iran, E-mail : [email protected]
VOLATILE OIL COMPOSITION OF CENTAUREA AUCHERI (DC.) WAGENITZ.
1
ALI ASADIPOUR,
2MITRA MEHRABANI,
2MOSLEM LARI NAJAFI
1
Department of Medicinal Chemistry,
2Department of Pharmacognosy, Faculty of pharmacy, Kerman University of Medical Sciences, Kerman, Iran
ABSTRACT
Centaurea aucheri (DC.) Wagenitz is one of the species of Asteraceae that has not been the subject of many investigations. Different species of this genus have been used in traditional medicine. In this investigation C. aucheri was collected from Khanesorkh of Kerman and the essential oil of the aerial parts of plant was extracted by Clevenger apparatus and analyzed by GC-MS. Identification of the components of oils were based on their retention indices and mass spectra data in comparison with those reported in literatures. The amount of essential oil was 0.16% and 22 substances consisting 80.03% of the composition of the essential oil were identified. The main compounds were caryophyllene oxide (19.44%), β-caryophyllene (14%), Geremacrene-D (13.38%). The essential oil was rich in sesquiterpene oil.
Keywords: Centaurea aucheri, Essential oil, GC- MS INTRODUCTION
The large genus Centaurea (Asteraceae, Cardueae) comprises about 500 species, which are predominantly distributed around the Mediterranean area and in west Asia (1). In Iran this genus has 74 annual to perennial herbaceous species that are widespread around the country (2). Some species of Centaurea genus such as C.
cyanus and C. scabosia have anti-pyretic, analgesic, cardiotonic activities and are useful for liver and skin diseases and relif of thestomach- ache (3, 4). Centaurea aucheri (DC.) Wagenitz is a perennial herb that approximately grows all over of the country (5). A literature search showed that no report on the analysis of secondary metabolites of this plant is available.
Studies on the volatile constituents are limited to C. cineraria subsp. umbrosa and C. napifolia (6), C. mucronifera and C. chrysantha (7), C.
pseudoscabiosa subsp. pseudoscabiosa and C.
hadimensis (8) and C. kotschyi var. kotschyi and C. kotschyi var. decumbens from Turkey(9), C.
pelia, C. thessala subsp. drakiensis, C.
zuccariniana, C. raphanina subsp. mixta, C.
spruneri from Greece (1,10) and C. calcitrapa and C. solstitialis from the USA (11,12,13). Other studies deal only with partially characterized essential oils of C. calcitrapa, C. gloriosa and C.
moschata (13-16).
Secondary metabolites which have been isolated from Centaurea species are: flavonoids, nor- isopernoides, elemanolides, elemanes, germa- crenolides and eudesmanolides (16-19), flavonoid
sulfate (20), sesquiterpene lactones (21, 22) and Indole alkaloids (23).
This investigation describes the volatile oil constituents of Centaurea aucheri (DC.) Wagenitz. from Iran.
MATERIALS AND METHODES Plant Material
The aerial parts of the wild-growing C. aucheri (DC.) Wagenitz. were collected during the flowering period from Khanesorkh, (Kerman Province, Iran) at an altitude of ca. 2500m in June 2002. The plant was identified as C. aucheri (DC.) Wagenitz. by Dr. Vahideh Nazeri in Bahonar university of Kerman and a voucher specimen of the plant (No. 1024) was deposited in the Herbarium of the Faculty of Pharmacy of Kerman university. The air-dried aerial parts of the plant were powdered and the volatile fraction was prepared by hydrodistillation (Clevenger) for 3 hours and then it was dehydrated with anhydrous sodium sulfate for GC-MS analysis (24).
GC/MS analysis
The oil was analyzed by GC/MS using a Hewlett Packard 6890 mass selective detector coupled to a Hewlett Packard 6890 gas chromatograph, equipped with a cross-linked 5% PH-ME siloxane HP5-MS capillary column (30 m × 0.25 mm, film thickness of 0.25 µm). Operating conditions were as follows: carrier gas, helium with a flow rate of 2 ml/min; column temperature, 60-275 ºC at
4 ºC/min; injector and detector temperatures, 280 ºC; injected volume 0.1 µl; split ratio, 1:50. The MS operating parameters were as follows:
ionization potential, 70 eV; ionization current, 1 A; ion source temperature, 200 ºC and resolution of 1000.
Identification of components in the oil were based on retention indices relative to n-alkanes and computer matching with the WILEY 275.L library, as well as by comparison of the fragmentation patterns of the mass spectra with those reported in the literatures (25-28).
RESULTS
Aerial parts of C. aucheri (DC.) Wagenitz.
yielded 0.16% (v /w vs. dried material) of oil with a strong aroma. Twenty-two components representing 80.03% of the total oil composition
were characterized and results with their percentage composition are listed in table 1. The major constituents of the sesquiterpene-rich oil of C. aucheri (DC.) Wagenitz. were caryophyllene oxide (19.44%), β-caryophyllene (14%), geremacrene-D (13.38%). The oil contains:
sesquiterpene hydrocarbons (50.1%) and oxygen- containing sesquiterpenes (27.24%).
Nearly 20 percent of the oil composition is unknown; which might be due to similarities of the pattern of their mass spectra of terpenoids or insufficient information about their RI in literatures. The mass spectra of main unidentified compounds (representing 12.94% of the total oil components) showed molecular ion peak at 220 m/z (fig. 1), which might be due to oxygen- containing sesquiterpenes (25).
Table 1. Components of the oil from the aerial parts of Centaurea aucheri (DC.) Wagenitz.
No. Compound RIa Percentage
1 1-octen-3-ol 979 0.03
2 δ-elemene 1338 1.54
3 α- ylangene 1372 0.54
4 α- copaene 1375 1.29
5 β- elemene 1391 1.13
6 β-caryophyllene 1427 14.00
7 γ-elemene 1440 5.16
8 Aromadendrene 1444 0.44
9 α-humulene 1456 1.90
10 β-farnesene 1464 1.53
11 Germacrene –D 1487 13.38
12 β-selinene 1492 1.35
13 Bicyclo germacrene 1499 3.12
14 β- bisabolene 1511 0.28
15 γ-cadinene 1515 0.55
16 δ-cadinene 1526 0.84
17 Unidentified 1529 0.38 18 Unidentified 1535 1.65
19 α-cadinene 1539 0.45
20 α-calacorene 1545 0.45
21 Germacrene –B 1558 2.15 22 Unidentified 1566 1.23 23 Caryophyllene oxide 1585 19.44
24 Unidentified 1615 1.41
25 4-Hexadecen-6-yne* 1629 2.66 26 Iso spathulenol* 1660 7.80 27 Unidentified ** 1673 5.47 28 Unidentified ** 1702 2.45 29 Unidentified ** 1713 4.99 30 Unidentified 1742 0.90 31 Unidentified 1791 0.68 32 Unidentified 1897 0.81 aRetention indices (RI) on HP5- MS capillary column.
* Tentatively identified.
** Mass spectra are showed in Figure 1.
40 60 80 100 120 140 160 180 200 220 240 260 280 0
50000 100000 150000 200000 250000 300000 350000 400000 450000 500000 550000 600000
m/z-->
Abundance
RI=1673 43
91
105 79
67 159
117 55
131
177
220 146
202
189 236 252 267 281 295
A
40 60 80 100 120 140 160 180 200 220 240 260 280
0 50000 100000 150000 200000 250000 300000 350000 400000 450000 500000
m/z-->
Abundance
RI=1713 43
91 109 79
55 159
67
121
135 220
177 147 202
189 240 256 268 281
B
40 60 80 100 120 140 160 180 200 220 240 260 280 300
0 50000 100000 150000 200000 250000 300000 350000 400000 450000
m/z-->
Abundance
RI=1702 41
91 55
77
105
131 159
117
177 220
145 192 205 232 244 262 279 298
C
Figure 1. Mass spectra of main unidentified compounds of the oil of C. aucheri (DC.) Wagenitz.
A: unidentified compound with RI=1673, B: unidentified compound with RI= 1713, C: unidentified compound with RI= 1702
DISCUSSION
A search through the literature (1, 6-16) showed that the amount of essential oil of C. aucheri (DC.) Wagenitz. (0.16%) is higher than C.
raphanina subsp. mixta and C. spruneri (both 0.01%) (1), C. cineraria L. subsp. umbrosa (0.02%) and C. napifolia (0.08%) (6), C.
mucronifera (0.09%) and C. chrysantha (0.09%)(7), and C. pelia, C. thessala subsp.
drakiensis and C. zuccariniana (all 0.05%) (10).
While C. aucheri (DC.) Wagenitz has a pale greenish volatile oil, another species have been reported (1,6,7,10) which have yellowish volatile oils.
Examination of the main volatiles which have been identified in Centaurea species (1, 6-16), show that C. moschata has a quite unique composition because of the presence of large amount of monoterpene (16), whereas in C.
aucheri (DC.) Wagenitz., C. pseudoscabiosa subsp. pseudoscabiosa, C. hadimensis, C. kotschyi var. kotschyi, C. kotschyi var. decumbens and C.
solstitialis have mainly sesquiterpenes (8, 11, 12, 13).
In C. pelia, C. thessala subsp. drakiensis and C.
zuccariniana, C. raphanina subsp. mixta such as C. aucheri (DC.) Wagenitz., monoterpene
hydrocarbons and alcohols are completely absent;
and main volatiles are caryophyllene oxide (1, 10).
Monoterpenes, likewise are almost absent in C.
chrysantha (7) and C. zuccariniana (10).
β-Caryophyllene is one of the main volatile constituents of C. raphanina subsp. mixta and C.
spruneri (1), C. cineraria subsp. umbrosa and C. napifolia (6), C. mucronifera and C.
chrysantha (7), C. pseudoscabiosa subsp.
pseudoscabiosa and C. hadimensis(8), C. kotschyi var. kotschyi and C. kotschyi var. decumbens (9) and C. solstitialis (11, 12, 13) such as C. aucheri (DC.) Wagenitz.
Germacrene-D is the major volatiles of C.
cineraria subsp. umbrosa (6), C. mucronifera and C. chrysantha (7), C. pseudoscabiosa subsp.
pseudoscabiosa and C. hadimensis (8), C.
kotschyi var. kotschyi and C. kotschyi var.
decumbens (9).
Diterpenes are not present in essential oil of C.
aucheri (DC.) Wagenitz., but are found in the essential oils of C. raphanina subsp. mixta (1), C.
pelia, C. thessala subsp. drakiensis , C.
zuccariniana (10), and C. cineraria subsp.
umbrosa , C. napifolia (6).
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